Report second-level domains for UMA on pin failure.

net/base/transport_security_state.h

Index: net/base/transport_security_state.h
===================================================================
--- net/base/transport_security_state.h	(revision 106614)
+++ net/base/transport_security_state.h	(working copy)
@@ -128,6 +128,12 @@
   static bool IsGooglePinnedProperty(const std::string& host,
                                      bool sni_available);
 
+  // Report UMA statistics upon pin failure. Reports only down to the
+  // second-level domain of |host| (e.g. google.com), and only if |host| is

[wtc, 2011/10/25 00:49:57]

The example should say something like
"google.com if |host| is mail.google.com".

+  // an IsPreloadedSTS host (or, if |sni_available|, an SNI preloaded STS

[wtc, 2011/10/25 00:49:57]

Nit: IsPreloadedSTS is a private method, so it probably shouldn't
be used in the comment for a public method.

+  // host).
+  static void ReportUMAPinFailure(const std::string& host, bool sni_available);

[wtc, 2011/10/25 00:49:57]

"PinFailure" needs to be more specific, such as "CertPinFailure"
or "PublicKeyPinFailure".

The comment on line 131 ("pin failure") needs a similar change.

Also, "ReportUMAPinFailure" sounds like we want to report
"UMA pin" failure.  I think we need to add "On":
    ReportUMAOnPinFailure
or remove "UMA":
    ReportPinFailure

+
   // Deletes all records created since a given time.
   void DeleteSince(const base::Time& time);